Method of bleaching linoleum using hydrogen peroxide bleach



FIF8509 DR 21969;?)82

Nov. 15, 1960 Filed May 13; 1955 INVENTOR I ADDISON W- KELLEY HAROLD A. REEHLING l LI A y ATTORNEY United States Patent METHOD OF BLEACHING LINOLEUM USING HYDROGEN PEROXIDE BLEACH Addison W. Kelley, Conestoga Township, Lancaster County, and Harold A. Reehling, Lancaster, Pa., assignors to Armstrong Cork Company, Lancaster, Pa., a corporation of Pennsylvania Filed May 13, 1955, Ser. No. 508,049

3 Claims. (Cl. 8-111) This invention relates to a method of bleaching a continuous web of sheet material, and more particularly to a method of bleaching pigmented floor and wall covering of the linoleum type using a chemical bleaching agent.

In the resilient floor and wall covering industry, considerable difiiculty has been experienced with discoloration of the material resulting from the stoving or maturing operation. This discoloration of linoleum type products is inherent in the materials used as a binder and in the curing cycle which the material must undergo to become tough enough for service as a flooring product. The effect of this discoloration is to reduce the brightness of the colors and generally lessen the sales appeal of the product to the consumer. The exact cause of the discoloration is not definitely known, but it is believed to result from the formation of certain unsaturated organic compounds forming chromophore groups on the surface of the material. Because of this resulting discoloration, a greater proportion of pigmenting color is necessary in order to attain the high standard of color required to produce distinctive color designs. Even with this increased pigment content, a certain amount of bleaching is necessary to restore the natural brilliance of the material which is matured for a relatively long period of time. In the past, this bleaching has been done by exposure to sunlight over prolonged periods of time, ranging anywhere from three to six hours, depending on the shade of the material. Lighter shades require a longer bleaching time. This is done by placing the material in conventional hot houses or laying it out in the open in the direct rays of the sun. These methods involve considerable expense in handling, and also the matter of determining the proper amount of bleaching is a more or less haphazard guess by a skilled artisan. Another disadvantage of sun bleaching is that the material will revert to its discolored appearance if removed from light for a prolonged period of time.

Some attempts have been made to utilize a chemical bleaching process on this material; however, prior chemical bleaching processes have been slow due to the dilute concentration of the commercially available bleaching solutions, making it necessary to expose the material to the bleaching solution for a relatively long period of time, ranging anywhere from 30 minutes to one hour. prolonged exposure to the bleaching solution had a deleterious effect on the binder system of the material being bleached, and also was entirely too slow for adaptation to the present high-speed production of materials of this type.

The present method involves a chemical bleach utilizing a relatively high concentration of hydrogen peroxide which can be quickly neutralized to form a water-soluble salt which can be easily rinsed from the surface of the material. As an example of a bleaching material suitable for carrying out this invention, we have found that an aqueous solution of alkaline hydrogen peroxide bleach, in which the peroxide solution is present in the amount of 35 gives desirable results.

This

2,960,382 Patented Nov. 15, 1960 A typical formulation is as follows: Percent by weight Water 18.1718 Hydrogen peroxide 75.7883 Sodium hydroxide 3.3475 Hydrated lime .1674 Sodium silicate .6250

Alkanol (alphylnaphthalene sodium sulfonate) (wetting agent) 1.6882

It will be seen from this formulation that the aqueous bleaching solution, of which 35% is the bleaching solution containing 7 5.7883% by weight of hydrogen peroxide, yields a resulting peroxide concentration of 75.7883% of 35 or about 27%.

In the preferred method, the 35 hydrogen peroxide solution is blended with the caustic solution comprising the sodium hydroxide and hydrated lime in a blending tank at a temperature ranging between 60 F. and 65 F. The 35 aqueous solution of hydrogen peroxide is normally stable, and in order to lend instability required for bleaching, the sodium hydroxide and hydrated lime are added to the peroxide. This lends the peroxide solution unstable, increasing the bleaching effect of the solution. While the above example recites sodium hydroxide and hydrated lime as the destabilizing agent for the peroxide, it will be understood that any relatively strong alkali can be utilized for carrying out this invention. This blending is accomplished in a closed tank and at a low temperature to prevent foaming of the material due to its unstable condition. The mixture of peroxide, sodium hydroxide, and hydrated lime is then piped to a second blending tank, where sodium silicate and the wetting agent are added. In order to prevent the material from foaming in the applicator pan, the sodium silicate stabilizing agent is added just before the material is delivered to the pan. The pan is also Water jacketed. The purpose of the Wetting agent is, of course, to enhance the distribution of the bleaching solution to the naturally oily surface of the material to be treated. Any of the commercially available Wetting agents may be used for this purpose.

In the ordinary utilization of peroxide bleaches, such as in the bleaching of cotton sheet material, rope, etc., it is customary to pass the material being bleached through a bath of the bleach and thereafter wash the excess bleaching solution from the material. In bleaching operations of this type, the bleach has no deleterious effect on the material being treated so the delicate controls developed for this invention need not be utilized in the bleaching of cotton, where the usual procedure is to expose the fabric to the bleach for a period sufliciently long to insure the removal of all the coloring matter. Overtreatment has no harmful effect. Also, the destabilizing agent in the cotton bleaching process is added in the tank in which the fabric is immersed and foaming is permitted. This is not the case in bleaching a finished pigmented product such as linoleum, in which a definite deleterious effect can result from overexposure to the bleaching solution. Such overexposure breaks down the binder system of the linoleum and renders the material unsuitable for service. It is, therefore, impossible to utilize the conventional system of applying high concentration peroxide bleach to a product of the linoleum type.

It has also been found through experimentation that it is desirable to uniformly apply a thin coating of bleaching solution to the surface of the material to insure a uniform quantity of bleach to all parts of the surface to be treated and to allow such bleaching solution to remain only on the surface for a predetermined controlled period of time, after which the bleaching solution is neutralized and the salts resulting from the neutralization step are washed from the surface of the material. In order to carry out this process, a roll-coating device is utilized as the preferred method of applying a uniform coating of the bleaching solution to the surface of the material. It will be understood that if the bleach is not uniformly applied, a greater amount of bleaching will occur in some areas than in other areas, and a sheetof ma-terialhaving uneven surface colorings will result, which is highly objectionable. After the uniform coating of bleaching solution is applied, the action ofthe bleaching solution is rapidly effected by subjecting the material with the applied bleach to an elevated temperature in the range of 230 F. to 270 F. to dry the bleaching solution while it is exposed to the surface of the material. This is accomplished by passing the material through a heating chamber at the rate of approximately 100 feet per minute. Immediately after the material emerges from the heating chamber, a dilute solution of acid is sprayed on the surface of the material to neutralize the bleaching material on the surface of the sheet. Any neutralizing acid is effective for accomplishing this purpose, and we have used a 1% solution of sulfuric acid as a satisfactory neutralizing agent. This forms a water-soluble salt which is washed from the surface of the material by a suitable spraying device, after which the excess water is removed from the material by means of rubber Squeegees or a series of air jets directed onto the surface of the sheet. The material then passes into a drier, where the excess moisture is removed from the surface.

Another reason why it is not desirable to pass linoleum or similar products through a saturating bath of the bleach arises from the fact that linoleum is on a felt or burlap carrier which would be deleteriously affected by the bleaching solution. It is, therefore, essential that the bleach be applied only to the surface.

g It will be understood, of course, that the chromophore groups which caused the discoloration on the surface of linoleum are present throughout the sheet material; however, if the surface is bleached to the desired appearance, after the material is installed and the surface wears off, the light bleaches the newly presented surface and the problem of discoloration is no longer apparent.

The effect of the bleaching solution on the material is to oxidize the unsaturated chromophore groups and also to bleach the wood flour or other cellulosic material present in the composition being bleached, which oxidation renders the chromophore groups colorless. It will be understood that the bleaching has no effect on the pigment component of the material; but by rendering the chromophore groups colorless and bleaching the cellulosic components, the pigments present in the material display a greater degree of brilliance. Since the bleaching solution oxidizes the chromophore groups, they remain in their oxidized state and do not revert to the discolored appearance when removed from the light for a period of time.

The method here under consideration has been found satisfactory for bleaching linoleum compositions such as linoleum sheet goods for floor and wall coverings, Linotile, which is a linoleum composition in tile form, fiooring material made from rubber compositions, bulletin board material made from cork with a glue binder, and cork tile.

The method set forth in this application is shown in the attached drawing in which the numeral 2 designates a roll coater for applying a film of bleach to the surface of the material 3. The material then moves into a bleach drying oven 4, in which the temperature is elevated to from 230 F. to 270 F. After the material leaves the oven 4, it passes under an acid spray head 5, which directs a spray of acid on the surface of the material to neutralize the alkalinity of the bleaching material. This neutralization process forms a salt on the surface of the material which is removed by the water spray 6 directed onto the surface of the material. The excess water is removed from the material by means of an air jet doctoring arrangement 7 which is directed on the surface of the material after the water spray has removed the salt. The material then passes through the drier 8, which removes the remaining moisture from the material. The bleached material is then ready for inspection and shipment.

It will be obvious from the above description that we have developed a process of chemically bleaching continuous webs of sheet material which removes the objectionable discoloration from the surface of the material in a rapid oxidation process which prevents the oxidizing agent from being exposed to the material for a period of time sufficient to deleteriously affect the binder system in the material. The process can be carried out with the normal production operating speeds of the industry today.

We claim:

1. A process for bleaching a discolored linoleum surface comprising applying to said surface an aqueous alkaline hydrogen peroxide bleaching solution containing about 27% hydrogen peroxide, based on the weight of the solution, and drying the bleaching solution-contacted surface at elevated temperatures.

2. In a method of bleaching a. continuous web of linoleum having a decorative wear surface comprising discolored pigments, the steps comprising applying to the decorative wear surface of the linoleum a film of an aqueous mixture containing a hydrogen peroxide solution, a caustic solution, a stabilizing agent, and a wetting agent in a uniform thickness over the entire decorative wear surface of the linoleum, increasing the temperature of the surface to which the mixture is applied to a temperature ranging between 230 F. and 270 F. to increase the speed of reaction of the mixture, applying a dilute solution of neutralizing acid to the mixture to form a salt residue on the decorative wear surface of the linoleum, and thereafter washing the salt residue from said surface of the linoleum.

3. In a method of bleaching a continuous web of linoleum having a decorative wear surface comprising discolored pigments, the steps comprising applying to the decorative wear surface of the linoleum a film of an aqueous mixture containing a 35% solution of hydrogen peroxide, sodium hydroxide, hydrated lime, sodium silicate, and a wetting agent in a uniform thickness over the entire decorative wear surface of the linoleum, increasing the temperature of the surface to which the mixture is applied to a temperature ranging between 230 F. and 270 F. to increase the speed of reaction of the mixture, applying a dilute solution of neutralizing acid to the mixture to form a salt residue on the decorative wear surface of the linoleum, and thereafter washing the salt residue from said surface of the linoleum.

References Cited in the file of this patent UNITED STATES PATENTS 2,029,985 Clark et a1 Feb. 4, 1936 2,194,358 Hundt et al Mar. 19, 1940 2,312,218 MacBean Feb. 23, 1943 2,510,595 McEwen June 6, 1950 2,598,580 McEwen May 27, 1952 2,613,579 McEwen Oct. 14, 1952 FOREIGN PATENTS 637,150 Great Britain May 10, 1950 OTHER REFERENCES Farmers Bulletin No. 1474, U.S. Dept. of Agri., Stain Removal from Fabrics, page 26, September 1942. 

1. A PROCESS FOR BLEACHING A DISCOLORED LINOLEUM SURFACE COMPRISING APPLYING TO SAID SURFACE AN AQUEOUS ALKALINE HYDROGEN PEROXIDE BLEACHING SOLUTION CONTAINING ABOUT 27% HYDROGEN PEROXIDE, BASED ON THE WEIGHT OF THE SOLUTION, AND DRYING THE BLEACING SOLUTION-CONTACTED SURFACE AT ELEVATED TEMPERATURES. 